More than 200 political leaders and other prominent individuals have signed an open letter to the European Union and United States urging them to take “emergency measures” to demand Russia release Ukrainian pilot Nadia Savchenko.

Svetlana Alexievich, the Nobel Prize Winner in Literature from Belarus, is among the signatories of the letter, which accuses Russian authorities of making a "mockery of civil rights, international law, and their own Constitution."

Savchenko says she was seized in eastern Ukraine in June 2014, while fighting with a volunteer battalion against Russia-backed separatists, and taken to Russia illegally.She is now on trial, accused of acting as a spotter who called in coordinates for a mortar attack that killed two Russian journalists.

Savchenko declared a hunger strike, refusing even liquids, on March 3 after the judge adjourned the trial for a week without allowing her to give her final statement.

Prosecutors have asked for Savchenko to be found guilty and sentenced to 23 years in prison. A verdict is expected later this week.

After receiving the letter, an EU spokeswoman described Savchenko's hunger strike as "very worrisome," and said that "Russia bears responsibility for the health, well-being, and observance of human rights of all persons it detains."

Ukrainian President Petro Poroshenko said in a Facebook posting that Savchenko was visited in her southern Russian detention center by Ukraine's consul-general on March 7.

Ukraine's Hromadske Radio website afterward posted a hand-written note that was signed by Savchenko and dated March 7.

"Whether dead or alive, I have already won," said the message. "I will leave jail on my own terms, showing the entire world that Russia may be forced into submission if you remain as fearless and unyielding as me."

Savchenko's supporters fear that her refusal to drink may irreparably damage her health or even kill her.

One of Savchenko's Russian attorneys said his client is suffering from "an accelerated heart beat, swelling legs, and jumps in temperature."

"She is still forbidding Russian doctors from performing any tests or medical procedures," lawyer Nikolai Polozov wrote on Facebook.